Copper [Cu] is the name of the common, abundant igneous mineral that occurs in nature in its native state, and as part of a number of other minerals, including sulfides (chalcocite and covellite); mixed sulfides with iron (bornite and chalcopyrite); and mixed sulfides with arsenic and antimony (enargite and tetrahedrite).
Archaeological evidence suggests that copper was exploited by humans at least 9,300 years ago. The discovery of a weathered ore deposit, and how to work the metal, was without a doubt a revolution. However, unalloyed copper was too soft to be useful as a significant source for tool or weapon construction. Instead, copper's original use was for decorative and perhaps religious ornaments. Copper deposits are located all over the world, and the ore was independently identified and worked many different times.
Copper Working Stages
The sequence and dating of the stages of sophistication in metal working in Southwest Asia is currently understood as follows:
- Hammering and annealing, ~7300 BC
- Reduction smelting, melting and casting, ~5000 BC
- Alloying with tin to produce bronzes, ~3700 BC
- Smelting of sulfide ores and cupellation, ~ 2500 BC
The earliest known evidence for copper working is at Cayönü Tepesi in what is today southeastern Turkey. There, by the late 8th/early 7th millennium BC, copper hooks, awls and sheet metal were produced. The copper used at Cayönü was very pure (98.8%) copper, and its source was likely the Ergani Maden copper region about 9 miles (15 kilometers) away.
There are also a handful of other sites in the Euphrates and Tigris rivers region and in highland Iran with evidence for copper working, but there is no real evidence of exchange until after smelting in invented and spread, in the 6th millennium BC. The first evidence of that is at Catal Hoyuk, in Turkey, ~6300-5500 BC. Smelting allowed the production of woodworking tools, such as celts and axes, the most famous of which is the copper axe of the Iceman, ca. 3200 BC.
Evidence of early smelting practices near major copper deposits in Iran and Anatolia, shows that the process involved roasting ores in small clay crucibles to produce ingots.
The invention and spread of copper smelting in Europe and Asia is one of the key characteristics of the period known to archaeologists as the Chalcolithic or Copper Age, ~4500-3500 BC.
Old Copper Complex
The Old Copper Complex is a series of cultures that originated in the Middle Archaic period of North America, and it represents North America's oldest metalworking, beginning about 7,000 years ago. Recent (Levine 2007) investigation of Archaic samples from 18 archaeological sites throughout the northeastern United States and southeastern Canada revealed that 78% of the copper samples were derived from Lake Superior sources in the midwestern state of Michigan, with many of the samples over 1,000 mi (1600 km) from the source.
The same study illustrated that, by comparison, some two thousand years later, Early Woodland groups had identified and were exploiting a far more diverse set of quarries, including several local copper deposits.
Iron Age Copper Production
During the height of the Late Bronze Age, copper production was controlled by Egypt, Mycenae and Hittite societies. After the decline of these societies, an abrupt increase in copper production in the Levant took place.
The flurry of copper production began as early as the 15th century BC, before the full collapse of the established and ruling societies. Evidence has been collected at Khirbat en-Nahas and Khirbat al-Jariya, two copper production sites in Wadi Faynan of Jordan (Ben-Yosef et al 2010), near the largest copper ore deposit in the southern Levant.
This production was likely instituted by local semi-nomadic tribal societies, which Ben-Yosef et al. suggest represent the Biblical "Edom".
A significant element of Mississippian societies (southeastern and midwestern United States, ~1050 AD to European contact), was the production of ceremonial and decorative copper items, including beads, hammered plates and copper-clad personal adornments. Copper artifacts associated with the Mississippian period have been identified at the capitals of Cahokia, Etowah, Spiro and Moundville, all of which participated in the elite network trade of prestige goods.
Based on excavations at Cahokia's Mound 34, Mississippian copper production included the obtaining of nuggets of naturally occurring copper from the Great Lakes or southeastern United States sources, deforming the nuggets by cycles of hammering and annealing into sheet and foil and then fashioning objects by molding, embossing, perforating and riveting the copper objects.
Investigation of CopperMany metallurgical techniques for copper analysis from archaeological sites have been developed in the past fifty years, including the development of PIXE spectrometry, and instrumental neutron activation analysis (INAA), both of which analyze the copper's component elements to help identify the sources and trade networks of copper objects.
Ben-Yosef E, Levy TE, Higham T, Najjar M, and Tauxe L. 2010. The beginning of Iron Age copper production in the southern Levant: new evidence from Khirbat al-Jariya, Faynan, Jordan. Antiquity 84(325):724–746.
Chastain ML, Deymier-Black AC, Kelly JE, Brown JA, and Dunand DC. 2011. Metallurgical analysis of copper artifacts from Cahokia. Journal of Archaeological Science 38(7):1727-1736.
Cooper HK. 2012. Innovation and Prestige Among Northern Hunter-Gatherers: Late Prehistoric Native Copper Use in Alaska and Yukon. American Antiquity 77(3):565-590.
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